U.S. patent number 7,446,047 [Application Number 11/061,350] was granted by the patent office on 2008-11-04 for metal structure with sidewall passivation and method.
This patent grant is currently assigned to Taiwan Semiconductor Manufacturing Company, Ltd.. Invention is credited to Yung-Cheng Lu, Minghsing Tsai.
United States Patent |
7,446,047 |
Tsai , et al. |
November 4, 2008 |
**Please see images for:
( Certificate of Correction ) ** |
Metal structure with sidewall passivation and method
Abstract
A passivated metal structure and a method of forming the metal
structure is disclosed. According to one embodiment, the patterned
metal structure, such as conductive lines, are formed on a
substrate. The copper lines are passivated by a polymer liner
between the copper lines and a low k dielectric filling the spaces
between the conductive lines. The polymer liner is preferably
deposited on the sidewalls of the conductive lines by
electro-grafting. The polymer liner may also be used in a damascene
process according to a second embodiment.
Inventors: |
Tsai; Minghsing (Chu-Pei,
TW), Lu; Yung-Cheng (Taipei, TW) |
Assignee: |
Taiwan Semiconductor Manufacturing
Company, Ltd. (Hsin-Chu, TW)
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Family
ID: |
36913319 |
Appl.
No.: |
11/061,350 |
Filed: |
February 18, 2005 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20060189143 A1 |
Aug 24, 2006 |
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Current U.S.
Class: |
438/700;
257/E21.273; 257/E21.581; 257/E21.264; 438/639; 438/597; 257/776;
257/773 |
Current CPC
Class: |
H01L
21/76835 (20130101); H01L 21/76834 (20130101); H01L
21/0226 (20130101); H01L 21/7682 (20130101); H01L
21/76831 (20130101); H01L 21/3127 (20130101); H01L
21/02118 (20130101); H01L 21/31695 (20130101) |
Current International
Class: |
H01L
21/311 (20060101) |
Field of
Search: |
;438/597,618,623,639,700,773,513,723,724,743,744,755,756
;257/773,776 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Balci, N., et al., "Electrically Conductive Polymer Grafts Prepared
By Electrochemical Polymerization of Pyrrole onto Poly[(methyl
methacrylate)-co-(2-(N-pyrrolyl) Ethyl Methacrylate)] Electrodes,"
Tr. J. of Chemistry, 22, 1998, pp. 73-80. cited by other .
Ozanam, F., et al., "Kinetics Of Electrochemical Grafting Of
Silicon With Organic Species,"
http://www.lure.u-psud.fr/VAS10/abstracts/O-08.pdf. cited by other
.
Frank, C.W., et al., "Center on Polymer Interfaces and
Macromolecular Assemblies," Final Report to the National Science
Foundation Materials Reseach Science and Engineering Center
Program, Jun. 26, 2003, pp. 1, 8, 11-14, 49-54. cited by other
.
"Passivation materials for polymer electronics," Fraunhofer ISC
Annual Report, 2002, pp. 46-47. cited by other .
Rappich, Dr. J., "Thin organic layers on silicon,"
http://www.hmi.de/bereiche/Se/vip/organics/projects/passivation.sub.--en.-
html, Aug. 10, 2003, pp. 1-2. cited by other .
Kalem, S., "Possible low-k solution and other potential
applications,"
www.eurosemi.eu.com/front-end/printer-friendly.php?newsid=5492,
Jul. 1, 2004, pp. 1-7. cited by other.
|
Primary Examiner: Dang; Phuc T
Attorney, Agent or Firm: Slater & Matsil, L.L.P.
Claims
What is claimed is:
1. A method of passivating sidewalls of a patterned metal structure
comprising the steps of: providing a substrate; forming patterned
metal structures over said substrate, said patterned metal
structures having spaces there between; depositing a low k
dielectric material over said substrate, said low k dielectric
material filling the spaces between said patterned metal
structures; and providing a protective polymer liner between
selective portions of said patterned metal structure and said low k
dielectric material by depositing said protective polymer liner by
electro-grafting, wherein said protective polymer liner is
deposited to a thickness of between about 5 .ANG. (angstroms) and
about 1000 .ANG. (angstroms).
2. A method of passivating sidewalls of a patterned metal structure
comprising the steps of: providing a substrate; forming patterned
metal structures over said substrate, said patterned metal
structures having spaces there between; depositing a low k
dielectric material over said substrate, said low k dielectric
material filling the spaces between said patterned metal
structures; and providing a protective polymer liner between
selective portions of said patterned metal structure and said low k
dielectric material, wherein said protective polymer liner
comprises a material selected from the group consisting of carbon,
fluorine, hydrogen, nitrogen, and oxygen, and wherein said
protective polymer liner is deposited to a thickness of between
about 5 .ANG. (angstroms) and about 1000 .ANG. (angstroms).
3. The method of claim 2 wherein said protective polymer liner is
N-succinimidyl acrylate and polypeptide.
4. The method of claim 1 wherein said protective polymer liner is
selectively deposited on the passivating sidewalls of said
patterned metal structure prior to depositing said low k dielectric
material.
5. The method of claim 1 wherein said protective polymer liner is
deposited as a blanket layer over said substrate and said patterned
metal structures prior to depositing the low k dielectric
material.
6. The method of claim 1 wherein said patterned metal structures
are patterned copper structures.
7. The method of claim 1 wherein at least a portion of said
patterned metal structures is formed as a damascene metal
structure.
8. The method of claim 1 wherein said low k dielectric material has
a dielectric constant of less than 3.0.
9. The method of claim 2 wherein said protective polymer liner is
selectively deposited on the passivating sidewalls of said
patterned metal structure prior to depositing said low k dielectric
material.
10. The method of claim 2 wherein said protective polymer liner is
deposited as a blanket layer over said substrate and said patterned
metal structure prior to depositing the low k dielectric
material.
11. The method of claim 2 wherein said patterned metal structures
are patterned copper structures.
12. The method of claim 2 wherein at least a portion of said
patterned metal structures is formed as a damascene metal
structure.
13. The method of claim 2 wherein said low k dielectric material
has a dielectric constant of less than 3.0.
Description
TECHNICAL FIELD
The present invention relates to patterned metal structures having
passivated sidewalls and formed on a semiconductor substrate. The
passivated sidewalls of the patterned metal structure are
particularly suitable for semiconductor structures subject to
oxidation during subsequent process steps. More specifically, the
invention relates to the use of a protective polymer lining
selectively deposited on the sidewalls to reduce or eliminate such
oxidation.
BACKGROUND
Increasing demands to reduce the geometry of semiconductor devices
while at the same time increasing the number of devices on a
semiconductor chip has resulted in significant changes in the
manufacturing process of semiconductors. For example, as the size
of the individual semiconductor elements on a chip decrease and the
number of elements increases, the capacitance between conductive
lines connecting elements has become a significant problem. To help
reduce the problem, copper, copper alloys and other highly
conductive metals are being used instead of aluminum.
Unfortunately, use of these metals in semiconductor devices
presents their own problems. For example, whereas in the past
aluminum could be deposited, patterned by a photoresist and then
etched to produce a desired conductive line structure, such
processes are not suitable for copper and most other high
conductive materials. Therefore, the damascene and/or dual
damascene processes are often used to form the conductive lines. In
addition, reduction of line to line capacitance with present day
devices also requires dielectric materials with very low k or
dielectric constants. For example, less than about 3.0.
Unfortunately, these dielectrics and especially the low k
dielectrics are very susceptible to the migration of copper ions
from the copper conductive lines into the dielectric. This, of
course is disastrous if the material is to be used as a
dielectric.
To stop the ion migration, there have been various attempts to
passivate the copper/dielectric material interface wherein such low
Ic materials are used to fill between the copper lines. For
example, certain conductivc metals and metal compounds such
tantalum. tantalum nitride, titanium, titanium nitride, and
tungsten do not themselves create major migration problems and can
be used as a barrier between the copper and the dielectric to stop
the copper ions from migrating. Of course, being a conductivc
material, these barrier metals must be carefully deposited so that
they cover only the copper and not the dielectric material.
Otherwise the conductive metal could cause shorts between
conductive lines or components that require cicetrical isolation
from each other. Therefore, referring to FIG. 1 and FIG. 2A, it is
seen that this prior art technique has been used where the barrier
metal 10 selectively adheres to the exposed copper sidewalls 12 of
the conductive lines 14a, 14b, and 14c while at the same time the
treated top surface 16 of the conductive lines 14a, 14b, and 14c
and the top surface 18 of the substrate 20 selectively avoid the
deposition of the baffler metal 10. Of course, if the "selectivity"
of the substrate and areas not intended to receive the barrier
metal 10 fails and the metal is unintentionally deposited in these
areas, electric shorts will be created.
Another prior art technique, as illustrated in FIG. 2B, includes
the depositing of a blanket layer of a high k dielectric material
22 aver the copper lines 14a, 14b, and 14c and the top surface 18
of the substrate 20. The high k dielectric material is selected to
be sufficiently dense to stop the ion migration, yet thin enough so
as not to significantly raise the over all dielectric constant of
the combination dense layer 22 of dielectric and the low k
dielectric that will fill between the conductive lines 14a, 14b,
and 14c to an unacceptable high value. This approach unfortunately
has several problems. First, there is poor adhesion between the
metal (such as copper) forming the conductive lines and the dense
dielectric. Second, a sufficiently dense dielectric will still
noticeably raise the dielectric constant of the combination of
materials. In addition, the deposition process is typically a high
temperature process that causes SM (Stress Migration) issues.
Therefore1 a process that retains a low k value That can be carried
out at a low or room temperature and still possess good adhesion to
metal would be advantageous.
SUMMARY OF THE INVENTION
These and other problems are generally solved or circumvented, and
technical advantages are generally achieved, by preferred
embodiments of the present invention, which include methods to
passivate the patterned conductive metal structures such as
conductive lines.
The passivation technique of the present invention comprises
forming a patterned metal structure such as conductive lines and/or
vias on the substrate, which includes spaces between different
parts of the structure or conductive lines. The patterned metal
structure is typically formed from a metal that is susceptible to
oxidation, such as for example, copper. According to one
embodiment, prior to depositing a low k dielectric over the
substrate and the patterned metal structure, including the spaces
between adjacent structure portions, a polymer liner such as a
nitrogen containing polymer. An example of a suitable polymer liner
is acrylate and polypeptide deposited preferably by
electro-grafting over at least any exposed metal portions, such as
sidewalls of the patterned metal structure. The polymer liner has a
low k value and is deposited at low temperatures and has excellent
adhesion qualities. Further, because the polymer liner is deposited
at low temperatures, there are no stress migration issues.
According to another embodiment, the polymer liner can be deposited
on the sidewalls of the vias and trenches formed in a low k
material for use with a damascene or dual damascene process.
The foregoing has outlined rather broadly the features and
technical advantages of the present invention in order that the
detailed description of the invention that follows may be better
understood. Additional features and advantages of the invention
will be described hereinafter, which form the subject of the claims
of the invention. It should be appreciated by those skilled in the
art that the conception and specific embodiment disclosed may be
readily utilized as a basis for modifying or designing other
structures or processes for carrying out the same purposes of the
present invention. It should also be realized by those skilled in
the art that such equivalent constructions do not depart from the
spirit and scope of the invention as set forth in the appended
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
For a more complete understanding of the present invention, and the
advantages thereof, reference is now made to the following
descriptions taken in conjunction with the accompanying drawing, in
which:
FIG. 1 shows a typical prior art semiconductor structure that
includes a patterned metal or copper conductive lines on a
substrate;
FIG. 2A illustrates the structure of FIG. 1 with a metal liner
selectively deposited on the sidewalls of the conductive lines
according to the prior art;
FIG. 2B illustrates the structure of FIG. 1 with a dielectric liner
blanket deposited over the substrate and the conductive lines
according to another prior art embodiment;
FIG. 3A illustrates the structure of FIG. 1 with a polymer liner
selectively deposited on the side walls of a conductive lines
according to the embodiment of the present invention;
FIG. 3B illustrates the structure of FIG. 1 with a polymer liner
blanket deposited over the substrate and the conductive lines
according to another embodiment of the present invention;
FIG. 4 illustrates further processing steps and structure suitable
for use with the structure of FIGS. 3A and 3B according to the
present invention;
FIG. 5 illustrates that the plasma liner may be deposited on the
sidewall surfaces of a low k dielectric material for use with both
a damascene and a dual damascene process;
FIGS. 6A, 6B, and 6C illustrate the process of depositing a poly
liner by electro-grafting for use with the present invention.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
The making and using of the presently preferred embodiments are
discussed in detail below. It should be appreciated, however, that
the present invention provides many applicable inventive concepts
that can be embodied in a wide variety of specific contexts. The
specific embodiments discussed are merely illustrative of specific
ways to make and use the invention, and do not limit the scope of
the invention.
Referring now to FIG. 3A there is illustrated a first embodiment of
the present invention. As shown, the prior art non-passivated
patterned metal structure of FIG. 1 now includes a non-conductive
polymer liner 24 selectively deposited on the sidewalls 12 only of
the patterned metal (copper) structure. As will be described
hereinafter, a layer of between about 5 .ANG. to about 1000 .ANG.
of polymer liner 24 is preferably deposited by electro-grafting to
the copper sidewalls. The polymer liner will typically be comprised
of carbon, fluoride, nitrogen, and oxygen. One suitable polymer
liner is N-succinimidyl acrylate and polypeptide. The use of the
selectively deposited polymer liner 24 as illustrated in FIG. 3A
provides a very important advantage over the prior art technique of
selectively depositing a barrier metal. Namely, if the
"selectivity" fails, (i.e. the polymer is deposited on unintended
surfaces), since the polymer layer is non-conductive, there is no
concern about electrical shorts.
In a similar manner, the polymer liner may also be deposited as a 5
.ANG. to 1000 .ANG. blanket layer 24a as illustrated in FIG. 3B.
Suitable polymers for such a blanker passivation layer is also
N-succinimidyl acrylate and polypeptide, and may be deposited by
electrografting. Use of a blanket polymer liner avoids
substantially all of the problem areas discussed above with respect
to FIG. 2B and the use of a dielectric blanket layer 22 for
passivation. Namely, the polymer has good to excellent adhesion
with the exposed metal. Further, the polymer is itself a rather low
k material and therefore the combined dielectric constant of the
polymer liner and the dielectric layer between the conductive lines
is not raised to an unacceptable level. The deposition takes place
at room temperature, and therefore there are no SM (Stress
Migration) issues.
FIG. 4 illustrates the blanket layer embodiment of FIG. 3B with a
low k or ultra low k dielectric 26 deposited over the conductive
lines 14a, 14b, and 14c and the substrate 20. For example, the
dielectric material will typically have a dielectric constant no
greater than about 3.0, and preferably between about 1.9 and 2.5.
As shown, the dielectric material 26 may be porous or include air
gaps such as the air gap 28a and 28b shown in FIG. 4. It should
also be appreciated that the composite structure in FIG. 4 is also
applicable to the embodiment of FIG. 3A wherein the polymer liner
is selectively deposited only on the exposed metal surfaces of the
conductive lines.
FIG. 5 illustrates that the use of a polymer material as a
passivation liner between the copper and a dielectric is also
applicable to a damascene or dual damascene patterned copper
structure. As shown in FIG. 5, the polymer liner 30 may be used to
passivate the interference between copper damascene structure 32
(includes conductive lines or traces 32a and connecting vias 32b)
from the dielectric layers 34a and 34b. The illustration also shows
a first metal layer 36 that could also be passivated by the polymer
liner 38 of the present invention.
Referring now to FIGS. 6A, 6B, and 6C, there is illustrated an
electro-grafting process for depositing the polymer liner. As shown
in FIG. 6A, a group of polymer molecules, such as molecule 40 that
include nitrogen ions 44 with a positive charge are attracted to
the negative charged electrode 42 (e.g. the exposed copper sidewall
discussed in FIG. 3A and shown in FIG. 6A). This electro activation
reduces the group of molecules by releasing the nitrogen ions,
which combine as N.sub.2 as shown in FIG. 6B. The reduced polymer
molecule 40a bonds with the negatively charged copper surface 42
(electrode) also shown in FIG. 6B. This process leaves a polymer
film bonded to and covering the exposed copper. The bonded polymer
molecules 40a themselves are then charged and attract and bond to
other polymer molecules such as molecule 40 as indicated in FIG.
6C. This "plating" process continues until the desired liner
thickness of between about a few nm (nanometers) to several .mu.m
(micro nanometers) is achieved. As previously discussed, a polymer
liner of between about 5 .ANG. to 1000 .ANG. is preferred.
Although the present invention and its advantages have been
described in detail, it should be understood that various changes,
substitutions and alterations can be made herein without departing
from the spirit and scope of the invention as defined by the
appended claims.
Moreover, the scope of the present application is not intended to
be limited to the particular embodiments of the process,
composition of matter, means, methods and steps described in the
specification. As one of ordinary skill in the art will readily
appreciate from the disclosure of the present invention, processes,
compositions of matter, means, methods, or steps, presently
existing or later to be developed, that perform substantially the
same function or achieve substantially the same result as the
corresponding embodiments described herein may be utilized
according to the present invention. Accordingly, the appended
claims are intended to include within their scope such processes,
compositions of matter, means, methods, or steps.
* * * * *
References